Sets the Cache-Control: no-cache header. Without a field name, the directive applies to the entire request and a shared (proxy server) cache must force a successful revalidation with the origin Web server before satisfying the request. With a field name, the directive applies only to the named field; the rest of the response may be supplied from a shared cache.

Private

Default value. Sets Cache-Control: private to specify that the response is cacheable only on the client and not by shared (proxy server) caches.

Public

Sets Cache-Control: public to specify that the response is cacheable by clients and shared (proxy) caches.

Server

Specifies that the response is cached only at the origin server. Similar to the NoCache option. Clients receive a Cache-Control: no-cache directive but the document is cached on the origin server. Equivalent to ServerAndNoCache.

ServerAndNoCache

Applies the settings of both Server and NoCache to indicate that the content is cached at the server but all others are explicitly denied the ability to cache the response.

ServerAndPrivate

Indicates that the response is cached at the server and at the client but nowhere else. Proxy servers are not allowed to cache the response.